I would think that compressing the code would result in less "efficiency" since it means the browser will have to do more processing in order to uncompress the code first.
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druciferreDec 18 '11 at 21:47

@druciferre I am not sure if browsers uncompress the code
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ajax333221Dec 18 '11 at 21:53

@druciferre, it depends on the compression methods. Some favor transmission time, and other favor parsing time. There are also ones in between that help with both.
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FakeRainBrigandDec 18 '11 at 21:53

@ajax333221, any compression that is done to HTML/CSS will virtually have to be done with JavaScript. So, unless you know of some other way?
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druciferreDec 18 '11 at 22:00

@FakeRainBrigand, I should have made my reasoning for quoting the word "efficiency" more apparent. By doing that I was implying different people have different views on what efficiency is. In my opinion, the time it takes to render the page once the code is downloaded is more important as most people have broadband and it takes very little time to get the code for a page.
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druciferreDec 18 '11 at 22:00

I didn't know about that way of doing it, it is interesting
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ajax333221Dec 18 '11 at 21:49

Honestly when it comes down to CSS just write out what you're thinking "I want to get rid of my old border, but then I want a top border" and just do it... that is until you realize CSS requires tons nested divs to position anything correctly ;)
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TomasDec 18 '11 at 21:53

I think you're asking the wrong question. The sample you provided is not going to result in much of a difference at all between download-times or the time it takes to render the page. I think any web-developer's main focus should be on making the code easily readable to at least themselves, and preferably to others.

I would have done this:

border-width: 1px 0 0 0;
border-style: solid; /* may not be necessary as many browsers use this as default */
border-top-color: #DDD;

It's short, and not very cryptic as to what the display is like, and doesn't do anything unnecessary.